Raptor plays a critical role in mTORC1 signaling. High expression of Raptor is associated with resistance of cancer cells to PI3K/mTOR inhibitors. Here, we found that OTUB1-stabilized Raptor in a non-canonical manner. Using biochemical assays, we found that the tyrosine 26 residue (Y26) of OTUB1 played a critical role in the interaction between OTUB1 and Raptor. Furthermore, non-receptor tyrosine kinases (Src and SRMS kinases) induced phosphorylation of OTUB1 at Y26, which stabilized Raptor. Interestingly, phosphorylation of OTUB1 at Y26 did not affect the stability of other OTUB1-targeted substrates. However, dephosphorylation of OTUB1 destabilized Raptor and sensitized cancer cells to anti-cancer drugs via mitochondrial reactive oxygen species-mediated mitochondrial dysfunction. Furthermore, we detected high levels of phospho-OTUB1 and Raptor in samples of patients with renal clear carcinoma. Our results suggested that regulation of OTUB1 phosphorylation may be an effective and selective therapeutic target for treating cancers via down-regulation of Raptor.

Raptor 在 mTORC1 信号传导中起着关键作用。Raptor 的高表达与癌细胞对 PI3K/mTOR 抑制剂的耐药性有关。在这里，我们发现 OTUB1 以非规范方式稳定了 Raptor。使用生化分析，我们发现 OTUB1 的酪氨酸 26 残基 (Y26) 在 OTUB1 和 Raptor 之间的相互作用中起着关键作用。此外，非受体酪氨酸激酶（Src 和 SRMS 激酶）在 Y26 处诱导 OTUB1 磷酸化，从而稳定 Raptor。有趣的是，OTUB1 在 Y26 处的磷酸化不影响其他 OTUB1 靶向底物的稳定性。然而，OTUB1 的去磷酸化使 Raptor 不稳定，并通过线粒体活性氧介导的线粒体功能障碍使癌细胞对抗癌药物敏感。此外，我们在肾透明癌患者的样本中检测到高水平的磷酸化 OTUB1 和 Raptor。我们的结果表明，OTUB1 磷酸化的调节可能是通过下调 Raptor 治疗癌症的有效和选择性治疗靶点。